Power storing apparatus

ABSTRACT

A power storing apparatus utilizes rotating flywheels. The casing of each flywheel is supported on the ground by an elastic member without fear of being rocked due to the rotation of a rotor. At least one pair of rotors, the rotors of which rotate in opposite directions to each other while producing the same rotation torque, is rotatably supported by a support supported on the ground through a suspending device which is capable of absorbing the vibration of an earthquake. Each rotor includes flywheels for maintaining the rotation of the corresponding rotor by an inertia force.

TECHNICAL FIELD

The present invention relates to a power storing apparatus for storingelectric power by a form of kinetic energy.

BACKGROUND ART

Studies have conventionally been made of a power storing apparatus forstoring electric power by a form of kinetic energy.

Such a power storing apparatus is composed of a rotor having flywheelsaround the rotary shaft, a stator provided with a coil for supplying adriving power for rotating the rotor and taking out the inductionelectromotive force generated by the rotation of the rotor, a bearingmeans for rotatably supporting the rotary shaft of the rotor, and acasing accommodating the stator, the bearing and the rotor. This type ofconventional power storing apparatus has a low earthquake resistance,because it is designed without leaving a surplus strength in order toreduce the friction loss of the bearing. Especially, in a bearingemploying the pinning effect of a type II superconductor, rigidity issubject to a gradient of a magnetic field and therefore low. Forexample, it is rocked about 1 to 2 mm due to a burden corresponding tothe weight of a rotor. In order to prevent the elements of the powerstoring apparatus from scattering at the time of an accident, theapparatus is often accommodated in a firm container.

There has also been an attempt at supporting the casing on the ground byan elastic member having a low spring constant in order to preventvibration, which is caused by an earthquake or the like and which maydislocate the rotor, from being transmitted from the ground to thecasing.

PROBLEMS TO BE SOLVED BY THE INVENTION

If the casing is supported by an elastic member having a low springconstant, as described above, then the counterforce of the rotation ofthe rotor which acts on the casing rocks the rotor, thereby making itdifficult to support the rotor stably.

OBJECT OF THE INVENTION

Accordingly, it is an object of the present invention to eliminate theabove-described problems in the related art and to provide a powerstoring apparatus which enables the casing to be supported on the groundwith elasticity and without a fear of being rocked due to the rotationof the rotor.

DISCLOSURE OF THE INVENTION

To achieve this aim, the present invention provides a power storingapparatus comprising: a plurality of rotors each including flywheels formaintaining the rotation of the rotor by the inertia force; and anelectric circuit for increasing or reducing the number of revolutions ofeach rotor so as to rotate the rotors in the opposite directions to eachother by the same rotational frequency, wherein at least one pair ofrotors is installed on the ground together with the correspondingbearings and casings through buffer devices.

According to a power storing apparatus of the present invention, sincethe number of rotations of one pair of rotors is controlled to beconstantly equal within plus or minus 1%, the torques as a counterforcefor fluctuating the input or the output cancel each other, so that thepower storing apparatus is prevented from rocking. In addition, sincethe power storing apparatus is supported on the ground by a soft springso that the natural or characteristic frequency of the apparatus is notmore than 0.3, the force transmitted from the ground to the apparatus atthe time of an earthquake is reduced to not more than 1/10.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structure of a characteristic part of a firstembodiment of a power storing apparatus according to the presentinvention;

FIG. 2 is a sectional view of the structure of one casing of the firstembodiment shown in FIG. 1;

FIG. 3 is an explanatory view of the first embodiment which is installedon the ground;

FIG. 4 is an explanatory view of the lower part of the supporting meansof the first embodiment with air springs disposed therein;

FIG. 5 is an explanatory view of the casings arranged in the block ofthe first embodiment;

FIG. 6 is a sectional view of a second embodiment of a power storingapparatus according to the present invention, explaining the casingsvertically arranged in the block;

FIG. 7 is an explanatory view of the second embodiment of a powerstoring apparatus according to the present invention which is installedin a concrete pit;

FIG. 8 is a plan view of the second embodiment shown in FIG. 7;

FIG. 9 is a schematic view of the electric system of the secondembodiment of a power storing apparatus;

FIG. 10 is a schematic view of the dynamic system of the secondembodiment; and

FIG. 11 is a graph of the transmissibility of vibration which changeswith a change of the natural frequency of the whole apparatus of thesecond embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention in the best mode will beexplained in the following with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a power storing apparatus according to thepresent invention. In FIG. 1, the reference numeral 1 represents a powerstoring apparatus having an output ability of 6000 Kwh. The powerstoring apparatus 1 of this embodiment is installed in a concrete pit 2formed in the firm ground shown in FIG. 3 and is provided with a steelblock 3 which constitutes a supporting means. The concrete pit 2 is inthe shape of a rectangular parallelepiped 11 meters square by 5 metersdeep.

The block 3, which is 10 meters square by 5 meters high and weighs 20 tin this embodiment, accommodates one pair of casings 4 and 5. The block3 is supported by 16 high-rigidity air springs 6a provided on the bottomsurface of the pit 2 and medium-rigidity air springs 6b provided on theside walls of the pit 2 so as to urge the block 3 sideways. The rigidityof the air spring 6a in the axial direction is 10 t/meter and the burdenthereof is 20 t. The burden of the air spring 6b is 10 t. It is possibleto use a rubber vibration insulator in place of the high-rigidity airspring 6a and to use a coil spring in place of the air spring 6b.

The rigidity of the block 3 in the horizontal direction is 40 t/meter.The inside of the block 3 is divided into square storing chambers 7a to7d by vertical walls 3c and 3d, and reinforcing girders 3b are erectedin the diagonal directions of the squares on the bottom surface 3a ofthe block 3. The casings 4 and 5 are disposed in the storing chambers 7aand 7b, respectively, which are divided by the vertical walls 3c and 3dand situated on the diagonal line of the square bottom surface 3a. Thecasings 4, 5 are mounted on the intersecting portions of the girders 3bin the storing chambers 7a and 7b, respectively, and the side surfacesof the casings 4, 5 are fixed to the vertical walls 3c and 3d by boltsor the like. An air exhausting system 8a as a radiator is placed in thestoring chamber 7c, and a control panel 8b for the power storingapparatus 1 is accommodated in the storing chamber 7d. The naturalfrequency of the block 3 in the horizontal direction is 0.2 Hz and thatin the vertical direction is 0.3 Hz. The frequency of the vibration ofan earthquake is not less than 1 Hz, which is not less than three timesof the frequency of the block 3. As it is clear from FIG. 11, whichanalyzes the transmission of vibration, that the external force of thefrequency not less than three times larger than the natural frequency isreduced to less than about 1/10, the block 3 is insusceptible to thevibration caused by an earthquake. When a rubber vibration insulator isused, the resistance to vertical rocking is insufficient, but since thevertical inertia force of 20 to 30% of the weight is only produced, thebearing can tolerate it. The upper part of the casings 4 and 5 are fixedto the upper lid 3e of the block 3, as shown in FIG. 5.

The casings 4 and 5 constitute one pair, and each has an outer diameterof 5 meters, a height of 4 meters and a weight of 20 t. The pair ofcasings 4, 5 function as a supporting means as an element of the block3. A rotor 9 having a weight of 30 t is rotatably supported in thecasing 4, as shown in FIG. 2. A bearing 10 for supporting the rotaryshaft 9a of the rotor 9 is provided on the upper wall of the casing 4,and flanges 12 for supporting the under surfaces of flywheels 11 of therotor 9 are projected toward the side wall of the casing 4. The holdingpower of the flanges 12 in the upward direction is 100 t, the supportingpower thereof in the downward direction is 10 t and the supporting powerthereof in the horizontal direction is also 10 t.

A groove is provided on a circumference at the central portion of eachof the flanges, and a superconductive pellet 13 is inserted into thegroove. The superconductive pellet 13 is cooled by liquid nitrogen by acooling device (not shown) provided within the flange 12. Thesuperconductive pellet 13 together with a magnet 14 constitutes abearing means for supporting the rotor 9 in a floated state. The rotor 9is floated by the repulsing forces caused by the cooled superconductivepellet 13 and the magnet 14. The casing 5 is also provided with a rotor9 which has the same mass and structure as those of the rotor 9 in thecasing 4.

An armature 16 which is driven when a driving coil 15 provided in thecasing 4 is energized is provided around the rotary shaft 9a of therotor 9. The driving coils 15 and the armatures 16 in the casings 4 and5 generate magnetic forces which rotate the rotors 9 in the oppositedirections to each other. In other words, when the rotor 9 in the casing4 rotates in the clockwise direction, in FIG. 1, the rotor 9 in thecasing 5 rotates in the counterclockwise direction at the same speed, sothat the torques generated by the rotors 9 in the casings 4 and 5 act inthe opposite directions to each other. Since the torques generated bythe rotors in the casings 4 and 5 and acting in the opposite directionsare the same, and the casings 4 and 5 are fixed to the block 3, thetorques generated by the rotations of the rotors 9 cancel each other, sothat the counterforce generated by the rotations of the rotors 9 are notapplied to the block 3 itself.

The flywheel 11 maintains the rotation of the rotor 9 as a whole by theinertia force when the energization of the driving coil 15 is stoppedafter the rotor 9 as a whole is driven by the driving coil 15. Byconnecting a load to the driving coil 15 when the rotor 9 as a whole isrotated by the inertia force, it is possible to take out the electricpower. In this embodiment, the rotor 9 has a generating power of 3000Kw. The effective facing area of one flywheel 11 for maintaining therotation of the rotor 9 is 2 m, and one flywheel 11 has an elevatingpower of 20 t, a lowering power of 2 t, and a horizontal convergingpower of 2 t. In this embodiment, the rotor 9 has five flywheels 11, sothat the flywheels 11 have an elevating power of 100 t in total.

According to the power storing apparatus 1 of this embodiment, whenthere is surplus power, if the rotors 9 are rotated by energizing thedriving coils 15 accommodated in the casings 4 and 5 in the block 3, therotors 9 are rotated at 4500 rpm at a maximum. At this time, although atorque of 8 tm is generated on each of the casings 4, 5, since thecasings 4, 5 are fixed to the block 3 and the rotors 9 having the samemass in the casings 4, 5 rotate at the same speed in the oppositedirections, the rotation torques generated by the rotors 9 cancel eachother. That is, no counterforce is generated in the block 3 by therotations of the rotors 9, so that the block 3 is prevented from rockingdue to the rotations of the rotors 9. Since the block 3 is supported inthe concrete pit 2 by the air springs 6a, 6b, the block 3 isinsusceptible to the vertical or horizontal vibration caused by anearthquake.

FIGS. 6 to 8 show a power storing apparatus 20 of a second embodiment ofthe present invention. Twenty power storing apparatuses 20 are installedin a substation of 100 m square and the load in the daytime and the loadin the nighttime are averaged. It is possible to store a power of 24000Kw×5 h in total.

In this second embodiment, the casings 4, 5 are arranged in the verticaldirection with one laid on top of another so that the rotary shafts 9aof the rotors 9 are situated on the same axis. One block thereforeconstitutes a supporting means. The rotors 9 of the casings 4, 5 havethe same mass and rotate in the opposite directions to each other at thesame speed. An adapter plate 21 is fixed to the upper part of each ofthe casings 4 and 5, and a flange 22 for fixing the casing 4 (5) isprovided at the lower part of each of the casings 4 and 5. The casings 4and 5 are united into one body by connecting the adapter plate 21 of thecasing 5 with the flange 22 of the casing 4 by bolts.

The power storing apparatus 20 is disposed in a cylindrical concrete pit24 having a diameter of 7 m and a depth of 10 m which is fixed to theground 23. The adapter plate 21 of the casing 4 which is laid on top ofthe casing 5 is suspended from the opening portion at the upper part ofthe concrete pit 24 by springs 25. The rigidity of the spring 25 is 10t/m and the burden is about 20 t. The casings 4 and 5 are suspended bytwelve springs 25 which extend in the radial directions, as shown inFIG. 8. The side wall portions of the casings 4 and 5 are pulled in thehorizontal directions by springs 26, 27 which extend in the tangentialdirections of the peripheral walls of the casings 4, 5. The springs 26,27 have a lower rigidity than the spring 25 and have a burden of about10 t. The springs 27 prevent a horizontal dislocation of the powerstoring apparatus 20, while the springs 26 lessen the torque of thepower storing apparatus 20. It goes without saying that air springs orrubber members are usable in place of the springs 26, 27. Alternately,the casings 4, 5 laid with one on top of another may be supported by airsprings on the bottom portion of the concrete pit 24 in the same way asin the first embodiment.

FIGS. 9 and 10 schematically show the electric-system and the dynamicsystem, respectively, of the power storing apparatus of the secondembodiment. In FIG. 9, an A/D transducer 30 is connected to the drivingcoil 15 which drives the armature 16 in the stationary state and whichtakes out the induction current of the armature 16 when it is rotated.An amplifier 31 (D/D transducer) is connected to the A/D transducer 30.A D/A transducer 32 is further connected to the amplifiers 31 of thecasings 4, 5. A generator 33 and a load 34 are connected to the D/Atransducer 32, and when the stationary armatures 16 are driven, theconnection between the generator 33 and the load 34 is cut off andcurrent is applied to the coils 15 so as to rotate the armatures 16 and,hence, the rotors 9. After the rotors 9 are rotated, the electricalconnection between the generator 33 and the D/A transducer 32 is cut offso as to rotate the rotors 9 by the inertia force. In order to take outthe electric power from the rotors 9 during the rotation of the rotors 9by the inertial force, the load 34 is connected to the D/A transducer32. Then, the induction current generated on the driving coils 15 istransduced into a direct current by the A/D transducers 30, andamplified by the amplifiers 31, transduced into an alternating currentby the D/A transducer 32, and input to the load 34. Each referencenumeral 35 represents a revolution counter for detecting the number ofrevolutions of the armature 16 and transmitting the data on the numberof revolutions of the armature 16 to the corresponding amplifier 31 as acontrol signal for the amplification when the rotors 9 are rotated. Whenthe rotors 9 are rotated by the inertia force, the revolution counters35 also transmit the data on the number of revolutions of the armature16 to the corresponding amplifiers 31 as control signals for theamplification.

FIG. 10 is a dynamic model for obtaining the natural frequency of thepower storing apparatus 20, and the following letters were inserted.With regard to the first apparatus, it is assumed that the mass of thearmature 3 is M11, the mass of the flywheel 5 is M12, and the mass ofthe casing 7 is M13. With respect to the second apparatus, M21, M22 andM23 can be obtained respectively. The spring constant of the spring 25is K1, the spring constant of the spring 27 is K2, the spring constantof the spring 26 is K3, the equivalent radius of the secondary moment ofthe flywheel 11 which acts on the rotary shaft 9a is R3, and thehorizontal distance between the center line of rotation of the rotaryshaft 9a and the position to which the spring 26 for lessening thetorque is attached is R4. The natural frequency A of the power storingapparatus 20 in the vertical direction, the natural frequency B thereofin the horizontal direction, and the natural frequency C in therotational direction are represented by the following equations:##EQU1##

FIG. 11 is a graph showing the relationship between the naturalfrequencies of the power storing apparatus 20 in the vertical,horizontal and rotational directions and the transmissibility ofvibration based on the above equations. The X-axis represents thenatural frequency of the power storing apparatus 20, and the Y-axisrepresents the transmissibility of vibration (%) lessened by the springs25, 26 and 27. In this graph, the frequency of the vibration of anearthquake is assumed to be 1 Hz.

According to this graph, the transmissibility of vibration reaches itsmaximum when the natural frequency (Hz) of the power storing apparatus20 including the springs 25, 26 and 27 is 1 Hz. When the naturalfrequency is increased to more than 1 Hz, the transmissibility ofvibration passes its peak and begins to reduce, but it remains aboveabout 1%. However, when the natural frequency of the power storingapparatus 20 is set at less than 1 Hz, the transmissibility of vibrationgreatly reduces, and when the natural frequency of the power storingapparatus 20 is 0.3 Hz, the transmissibility of vibration becomes about0.1%.

In other words, when the natural frequencies of the power storingapparatus 20 in the vertical, horizontal and rotational directions areset at not more than 0.3 Hz, respectively, the transmissibility ofvibrations in the vertical, horizontal and rotational directions is notmore than 0.1%, respectively. Therefore, if the natural frequencies ofthe power storing apparatus 20 in the vertical, horizontal androtational directions are set at not more than 0.3 Hz, respectively, theratio of the transmission of the vibration such as an earthquake to thepower storing apparatus 20 is greatly reduced, so that the stability issecured even if the rotors 9 are rotated at a high speed.

In this way, according to this embodiment, since the casings 4, 5 areaccommodated in the cylindrical concrete pit 24 with one laid on top ofanother, the power storing apparatus 20 not only has the same advantagesas that of the first embodiment but also is further advantageous in thatthe safety is secured against an unlikely accident such as thedislocation of the casings 4, 5.

Industrial Applicability

As described above, according to a power storing apparatus of thepresent invention, even if the revolutions of a pair of rotors areaccelerated or reduced when electric power is stored or discharged, therotation torques as the counterforces of the rotors which aretransmitted to the casings cancel each other, so that the power storingapparatus as a whole is prevented from rocking. In addition, since thepower storing apparatus is supported on the ground by soft springs, theforce transmitted from the ground to the apparatus at the time of anearthquake is very small, so that the risk of the rotors, the casings,the bearings, etc. being broken is greatly reduced. That is, accordingto the present invention, it is possible to design and produce a slimpower storing apparatus having a small friction loss without loweringsafety.

I claim:
 1. A power storing apparatus comprising:at least one pair of rotors, said rotors rotating in opposite directions while producing the same rotation torque; at least one pair of casings, each of said casings defining a volume within which one of said rotors is rotatably supported; resilient means, interposed between said casings and the ground, for supporting said casings and absorbing vibration of an earthquake; each of said rotors including a rotary shaft providing support within one of said casings and flywheels, for maintaining rotation of said rotors by inertial forces, axially spaced along said rotary shaft and extending outward from said rotary shaft; flanges in said volume defined by each of said casings and extending inward toward said rotary shaft from said casing, each of said flanges having a pair of said flywheels disposed adjacent to upper and lower surfaces thereof; means for generating magnetic forces which rotate the rotors in said opposite directions; superconductive pellets fixed on the upper surfaces of said flanges; and magnets provided on lower surfaces of said flywheels, each of said magnets facing one of said superconductive pellets so as to define one of a plurality of bearings by which said rotors are supported within said casings.
 2. A power storing apparatus according to claim 1, wherein the rotary shafts of the rotors of said at least one pair of rotors are parallel to each other.
 3. A power storing apparatus according to claim 1, wherein the rotary shafts of the rotors of said at least one pair of rotors are situated on the same axis. 